Reward Processing in Psychiatric Inpatients With Depression

Previous neuroimaging studies have investigated reward-processing dysfunction in major depressive disorder and have led to the common finding that major depressive disorder is associated with reduced reward responses within the reward circuit. Yet it is unclear whether such reward-processing dysfunction is specifically associated with the severity of depressive symptoms in major depressive disorder or is associated with common comorbidities.

We investigated reward-processing differences using a classic juice-delivery functional magnetic resonance imaging experiment to compare psychiatric patients with severe depressive symptoms (DEPs) to both psychiatric control subjects (PCs) and healthy control subjects. In this study, the DEPs (n = 108) were matched to healthy control subjects (n = 62) for demographic characteristics and to the PCs (n = 108) for demographics and comorbid psychiatric diagnoses. An a priori region of interest, the left putamen, was selected using previous studies. An exploratory whole-brain analysis was performed to explore for nonhypothesized regions.

Relative to the PCs and healthy control subjects, the DEP group showed smaller responses to reward stimulus in the left putamen. Whole-brain exploratory analysis revealed that DEPs had significantly lower responses to reward stimulus in the bilateral dorsal striatum (putamen and caudate), middle frontal gyrus, left precentral gyrus, and middle cingulate cortex than PCs.

Our findings suggest that DEPs may have a lesser ability to modulate behavior as a function of reward, especially in those individuals who experience the most severe depressive symptoms. In both DEPs and PCs, the severity of depressive symptoms was related to reduced reward responses in the left putamen.